Electron discharge apparatus



A. M. SKELLETT ELECTRON DISCHARGE APPARATUS Feb. 22, 1938.

Filed Feb. 26, 1937 FIG 2 T0 UTIL IZA TION CIRCUIT lNl/ENTOR AM.SKELLETT ATTORNEY Patented F eb. 22, 1938 UNITED STATES rarsn'r orricTelephone Laboratories,

incorporated, New

York, N. 351., a corporation of New York Application February 26, 11937,denial No. M737? 1% @lairns.

This invention relates to electron discharge apparatus and moreparticularly to such appa ratus especially suitable for the generationof ultra-high frequency oscillations.

One object of this invention is to enable the generation of oscillationsof extremely short wave-lengths.

Another object of this invention is to simplify ultra-high frequencyelectron discharge apparatus.

A further object of this invention is to facilitate the production of anegative resistance in the plate circuit of an electron dischargedevice, enabling the device to oscillate.

In one illustrative embodiment of this invention, an electron dischargedevice comprises a cathode, a plate electrode surrounding the cathodeand a plurality of successively arranged grid electrodes between thecathode and the plate electrode. The inner surface of the latter may betreated or coated to facilitate copious emission of secondary electronstherefrom. The plate electrode is operated at a positive potential withrespect to the cathode and the outer grid electrode is operated at apositive potential higher than that upon the plate electrode. Thepotentials on the various electrodes preferably are so related that thedevice operates upon the negative slope portion of the platevoltage-plate current characteristic and, more particularly, about apoint in this characteristic corresponding to such conditions that thesecondary electron current from the plate electrode to the outer grid isequal to the primary electron current tothe plate electrode and theplate electrode current decreases as the potential of this electrode isincreased.

In accordance with one feature of this invention, the plate electrode isprovided with a substantially cylindrical portion forming an induct.-anoe, and with other portions forming a capacitance whereby a tunedcircuit is completed within the enclosing vessel of the electrondischarge device.

In accordance with another feature of this invention, means are providedfor producing magnetic fields, of opposite polarity or directionadjacent spaced portions of the plate electrode. The current circulatingin-the plate electrode produces magnetic fields which augment the fieldadjacent one portion of the plate electrode and oppose the fieldadjacent another portion of the plate electrode. Consequently, thesecondary electron current from one portion of the plate electrode isdecreased and the secondary electron current from another portion ofthis electrode is increased thereby supplying a negative resistance tothe tuned circuit so that oscillations will be produced therein.

The invention and the foregoing and other features thereof will beunderstood more clearly and fully from the following detaileddescription with reference to the accompanying drawing in which:

Fig. l is a view in perspective of electron discharge apparatusillustrative of one embodiment of this invention, a portion of one ofthe magnets and of the enclosing vessel and plate electrode being brokenaway to show the electrodes more clearly;

Fig. 2 is a top view in cross-section of the apparatus illustrated inFig. l and showing an external conductor for coupling a utilizationcircuit to the oscillating circuit; and

Fig. 3 is a circuit diagram showing the external connections betweenthe'electrodes of the electron discharge device illustrated in Figs. 1and 2.

Referring now to the drawing, the electron discharge device there showncomprises an evacuated enclosing vessel H], which preferably is ofrelatively small height, having opposite substan- 2 type and comprise acylindrical metallic sleeve 0 it, having a coating of thermionicmaterial upon its outer surface, supported by a rigid conductor itsealed in the end wall H and aflixed to an integral extension E5 on thesleeve it. A heater element it including, for example, a filament I! isenclosed by the cathode sleeve it, the ends of the filament beingconnected to suitable leadingin conductors lfl'sealed in the end wall llof the enclosing vessel.

The cathode is encircled by a cylindrical inner grid coaxial therewithwhich may comprise a pair of annular conductive end members It and aplurality of equally spaced metallic rods or wires 2!] disposed parallelto one another and to the cathode and amxed to the annuli l9. One of therods 01' wires 20 may have an integral extension 2i sealed in the baseor end wall 1 H! of the enclosing vessel.

Disposed about the grid above describedand coaxial therewith is a secondgrid which may comprise annular conductive end members 22 and aplurality of equally spaced metallic rods or wires 23 aflixed to the endmembers 22 and ar-' ranged parallel to one another and to the oathode.Preferably the wires or rods 23 are mounted in radial alignment with thecorresponding wires or rods 20 01' the inner grid, as shown clearly inFig. 2. The outer grid may be supported by an integral extension 24 ofone of the rods or wires 23, sealed in the end wall or base I 2 of theenclosing vessel.

The outer grid 23 is encompassed in turn by a plate electrode includinga split substantially cylindrical portion 25 coaxial with the cathode I3and supported by a metallic rod or wire 26 sealed in the base or endwall l2 of the enclosing vessel and connected to the plate electrode atthe midpoint thereof. The inner surface of the cylindrical portion 25preferably is coated with a material having good secondary electronemitting properties. The plate electrode is provided also with a pair ofparallel conductive plates 21 ailixed, for example, to flanges 28 on thecylindrical portion 25. The plates 21 form a condenser and thecylindrical portion 25 forms an inductance in series with the condenserand constitutes therewith the oscillating circuit of the device. Anexternal utilization circuit may be coupled to the oscillating circuitas by a looped conductor 3! encircling the vessel 10.

Mounted about the enclosing vessel are two horseshoe magnets 29 and 30the poles of which preferably are located in proximity to thecylindrical portion 25 of the plate electrode so that concentratedfields obtain in the region between the inner surface of the plateelectrode and the outer grid. The two magnets are so constructed thatthe fields thereof are of substantially equal intensity and have theirpoles arranged oppo? sitely so that the fields are opposite indirection. That is to say, the north pole of each magnet is opposite thesouth pole of the other magnet so that, as indicated, for example, inFig. 1, the field of the magnet 29 is immediately adjacent the lefthandportion or half of the plate electrode and downward in direction whereasthe field of the magnet 30 is immediately adjacent the righthand portionor half of the plate electrode and upward in direction.

As shown in Fig. 3, the inner grid may be biased negatively with respectto the cathode, as by a battery 32, through a coil 33, which may be thesecondary winding of an input transformer T. The outer grid and theplate electrode may be maintained at positive potentials with respect tothe cathode, as by a battery 34, the potential applied to the outer gridbeing greater than that applied to the plate electrode and preferably ofthe order of several hundred volts.

During operation of the device, primary electrons emanating from thecathode l3 are attracted toward the outer grid 23 and the plateelectrode 25. Some of these electrons, because of their high velocities,will pass between the wires or rods 23 of the outer grid and impingeupon the plate electrode, as a result of which secondary electrons willbe released from the plate electrode. Some of these electrons thusproduced will flow to the outer grid because of its higher potentialwhile others will return to the plate electrode. Preferably the fieldsproduced by the magnets 29 and 30 and the potentials applied to theouter grid and the plate electrode are such that-for steady stateconditions the primary electron current to the plate electrode and thesecondary electron current from the plate electrode to the outer gridare substantially equal and the resultant plate electrode current whenvaried decreases as the potential of this electrode is increased.Inasmuch as the fields of the magnets 29 and 30 are of equal intensity,as described heretofore, the secondary current to the outer grid fromthe left-hand half and the right-hand half (in Figs. 1 and 2) of theplate electrode will be of substantially equal magnitude.

When the steady state condition is disturbed, as occurs actually whenthe potentials are applied to the electrodes of the device, a currentcirculates in the circuit composed of the cylindrical portion 25 of theplate electrode and the condenser plates 21'. This current producesmagnetic fields which oppose the field of one of the magnets 29 and 30and aid the field of the other of the magnets. At that portion or halfof the plate electrode wherein the circulating current produces a fieldaiding the field of the associated magnet, fewer secondary electronsflow to the outer grid so that in efiect the resultant current in thisportion is increased. Conversely, at that portion of the plate electrodewherein the circulating current opposes the field of the associatedmagnet, more secondary electrons leave this portion and flow to theouter grid so that in eflect the resultant current in this portion isdecreased. Consequently, a negative resistance is supplied to thecircuit composed of the cylindrical portion 25 of the plate electrodeand the condenser plates 21 as a result of which an oscillating currentis produced in this circuit. A similar oscillating current will obtainin a utilization circuit coupled to the internal circuit by theconductor 3|. The oscillating current may be modulated through theagency of the inner grid 20.

Inasmuch as the cylindrical portion 25 and condenser plates 21constituting the oscillating circuit may be made of small dimensions,the impedances of this circuit may be correspondingly small so that theinternal circuit may be resonant and oscillable at extremely highfrequencies.

Although a specific embodiment of the invention has been shown anddescribed, it will be understood, of course, that various modificationsmay be made therein without departing from the scope and spirit of thisinvention as defined in the appended claims. For example, although acoil has been shown for inductively coupling a utilization circuit tothe oscillating circuit, capacitive coupling means may be employed.Also, a di-electric medium, such as mica, may be interposed between thecondenser plates 21.

What is claimed is:

1. Electron discharge apparatus comprising a. cathode and an outputelectrode, said output electrode having a cylindrical electron receivingportion encompassing said cathode and defining an inductance, and havingalso spaced portions forming a capacitance in circuit with saidinductance.

2. Electron discharge apparatus comprising a cathode, a, grid, a plateelectrode encompassing said cathode and grid and having a cylindricalportion coaxial with said cathode, said cylindrical portion having aslot therein, and a pair of plate members mounted on said portionadjacent said slot and spaced to form a condenser.

3. Electron discharge apparatus comprising a cathode, a gridencompassing said cathode and coaxial therewith, a plate electrodeencompassing said cathode and grid, said plate electrode having a splitcylindrical portion coaxial with said cathode and defining aninductance, the inner surface of said portion being adapted to emitsecondary electrons, and a pair of spaced plate members mounted on saidcylindrical portion and forming a condenser in series with saidinductance.

4. Electron discharge apparatus comprising a cathode, a grid, a plateelectrode having a portion defining an inductance and having the surfacethereof toward said cathode adapted to emit secondary electrons, meansforming a condenser in circuit with said inductance, means applyingpositive potentials to said grid and plate electrode, the potential onsaid grid being greater than that upon said plate electrode, and meansfor producing spaced magnetic fields adjacent said surface, the fieldadjacent one portion of said surface being opposite in direction to thefield adjacent another portion of said surface.

5. Electron discharge apparatus in accordance with the next precedingclaim wherein said potentials and said fields are of such magnitudesthat for steady state conditions the primary elec-' tron current to saidplate electrode from said cathode and the secondary electron current to,

said grid from said plate electrode are substantially equal.

6. Electron discharge apparatus in accordance with the second precedingclaim wherein said field producing means comprises two magnets havingtheir poles adjacent oppositeedges of said plate electrode, the northpole of each magnet being in juxtaposition to the south pole of theother magnet.

'7. Electron discharge apparatus comprising a cathode, a gridencompassing said cathode, a plate electrode including a cylindricalportion encompassing said grid and having its inner sur face adapted to.emit secondary electrons, said cylindrical portion having a dividingslot therein, plate members mounted on said portion adjacent said slotand forming a condenser, means for maintaining said gridand plateelectrode positive with respect to said cathode, means for producing amagnetic field in one direction adjacent said cylindrical portion and toone side of said slot, and means for producing a magnetic field in theopposite direction adjacent said cylindrical portion and to the otherside of said slot.

8. Electron discharge apparatus in accordance with the next precedingclaim in which said field producing means comprises a pair of magnetshaving their poles adjacent opposite edges of said plate electrode.

9. Electron discharge apparatus comprising a cathode, a gridencompassing said cathode. a

plate electrode having a cylindrical portion coaxial with said cathodeand defining an inductance, the inner surface of said portion beingadapted to emit secondary electrons, means defining a capacitance inseries with said inductance, means maintaining said grid and said plateelectrode at positive potentials with respect to saidcathode, and meansfor producing substantially equal magnetic fields adjacent and parallelto opposite halves of said portion, the fields adjacent said halvesbeing opposite in direction.

10. Electron discharge apparatus comprising a cathode, a grid, a tunedcircuit consisting of an electrode in cooperative relation to saidcathode and said grid, said electrode being adapted to emit secondaryelectrons when primaryelectrons from said cathode impinge thereon, andmeans for differentially controlling the secondary electrons emittedfrom spaced portions of saidelectrode.

11. Electron discharge apparatus comprising a cathode, a grid, a plateelectrode having a cylindrical portion encompassing said cathode andsaid grid and defining an inductance, means defining a capacitance incircuit with said inductance and forming a tuned circuit therewith, theinner surface of said cylindrical portion being adapted to emitsecondary electrons, and means for differentially controlling thesecondary electrons emanating from opposite halves of said cylindricalportion.

12. Electron discharge apparatus comprising an enclosing vessel 'housinga cathode, a grid encompassing said cathode, a plate electrode having acylindrical portion coaxial with said cathode adapted to emit secondaryelectrons, and means defining a condenser in circuit with saidcylindrical portion and defining an oscillable circuit therewith, meansfor applying a positive potential to said plate electrode and a higherpositive potential to said grid, a permanent magnet having its polesadjacent opposite edges of substantially one half of said cylindricalportion, and a second permanent magnet having its poles adjacentopposite edges of the other half of said cylindrical portion, saidmagnets being of substantially the same strength and the field of onebeing opposite in direction to that of the other.

ALBERT M. SKELIE'I'I'.

